CNC single point threading, RH and LH (tech)

[JeepinDoug]

I realize this is a bit more than any garage fabber can do yet I think many people would be interested in seeing this.
Single point threading is done on geared lathes, chaser lathers or CNC for the most part. It's one single cutting tooth tool that cuts a thread, internal, external, right hand or left.
For a machinist it's easier to make a tool like this than fork out the bucks for a tap, two if you're making a turn buckle and large taps are pricey.
The single point tool has a 60* included angle with a slightly truncated tip, the tip has a flat just a few thousanths wide. This tool will make multiple passes at a few thousanths at a sweep, slowly generating the threads to sizes.
I'll go through the procedure how I made my steering links today.
Material; 7075T6 aluminum
Thread size; .875"-14tpi by 2.0" deep
Machine; Hardinge T42 w/Fanuc 18T control
I started by cutting my material blanks to 1/16" longer than my finished length.
I colleted over the Al to a certain length and drilled a 3/4" diameter hole 2.5" deep.
http://i15.photobucket.com/albums/a374/JeepinDoug/Threading/Drill.jpg
Drilled
http://i15.photobucket.com/albums/a374/JeepinDoug/Threading/Drilled.jpg
Next was rough and finish turning the diameterwith a nice radius on the corner.
http://i15.photobucket.com/albums/a374/JeepinDoug/Threading/Turn.jpg
Turned
http://i15.photobucket.com/albums/a374/JeepinDoug/Threading/Turned.jpg
For 3A class threads the hole needed to be bored to .802". A .060" corner break on the ID insures the threading tool doesn't blow a crappy burr out the front.
http://i15.photobucket.com/albums/a374/JeepinDoug/Threading/Bore.jpg
Bored
http://i15.photobucket.com/albums/a374/JeepinDoug/Threading/Bored.jpg

Continuing in next post.............

[JeepinDoug]

Okay.........

Here's the tough part since I have no experience single pointing a left hand internal thread.
The tool I had was carbide shaft with a brazed micrograin tip but the shank diameter was just thin for this deep of a thread. A chattered thread was the end result. I was able to clean it up but I hate this kind of finished part. I have a new tool I made that is a 5/8" diameter shank with a micrograin brazed tip.
Here's the small one I used;
http://i15.photobucket.com/albums/a374/JeepinDoug/Threading/Threadingtool.jpg
Ready to thread;
http://i15.photobucket.com/albums/a374/JeepinDoug/Threading/Thread.jpg
Threaded
http://i15.photobucket.com/albums/a374/JeepinDoug/Threading/Threaded.jpg
I did the same thing for the right hand threads but the machine program needs a very small alteration.
The machine's spindle is rotating CCW, the tool needs to cut from the outside in for righthand threads and from the inside out to cut lefthand threads. Because the lefthand threading needs to start from the inside the hole needs to be deeper, it's a feedrate lag issue.
The part turned out decent with good threads at Class 3A specs;
http://i15.photobucket.com/albums/a374/JeepinDoug/Threading/RHthread.jpg
This perticular machine has a nice graph display that will dry run on the screen to show you if you have any bad program inputs.
http://i15.photobucket.com/albums/a374/JeepinDoug/Threading/Graph.jpg
The link assembled fine.
http://i15.photobucket.com/albums/a374/JeepinDoug/Threading/Assembled.jpg
Another finished part on the buggy.
http://i15.photobucket.com/albums/a374/JeepinDoug/Threading/Installed.jpg

This is what I do on my vacation, I go to work :rolleyes:

[ProJunkRacing]

That is pretty cool , if you have access to the right equipment.

[jnutter]

Nice. I've done some internal single point threading on my manual lathe. Did a similar trick for the tool, except that i started with an HSS boring bar and ground the 60 deg. angle on it. Wouldn't want to try to thread to the bottom of a blind hole with my lathe though...

[m016324]

Nice. I've done some internal single point threading on my manual lathe. Did a similar trick for the tool, except that i started with an HSS boring bar and ground the 60 deg. angle on it. Wouldn't want to try to thread to the bottom of a blind hole with my lathe though...

It's not that hard you just keep track of the depth of the tool with an indicator. Granted it's not as easy as with a CNC machine but it's definately doable especially on aluminum as you can take bigger cuts per pass. Threading is definately not on the average hobbiest list of things they do but it's cool to see someone give a step by step even if it's a little over most hobbiest's equipment.

-ben

[solarpower]

good stuff.

CNC is the only way to fly. :smokin:

picking up a carbide insert bar with a threading tool might be worth the coin if you want to do a bunch more threads.

Not knocking your cutter BTW, it looks as good as most Toolmakers would make by hand, including myself.

[CJeep77]

When threading on my manual lathe, I flip the tool upside down when turning to a shoulder or blind hole and reverse the spindle. Eliminates the chance of crashing the tool!

[d.d.machine]

Doug try threading in CW but thread from the inside out for left`y threads
, I do a lot on internal
threading and pull the bar out on 90% of it. it brings the chips with it and I quit crashing bars .
P.S. it chatters a lot less do to the pulling and not pushing on the bar.

[JeepinDoug]

That's how I did it Duffy.
Today I went in and finished a beefier threading tool, 5/8" carbide endmill with a brazed carbide tip and ground for threads. I use a swiss tool grinder so it's not really by hand.
I threaded internal and external, right and left hand threads with the same tool. External just meant flipping the tool so I was on the right side of the material and changing the spindle direction for the cut.
I made a threaded spud so I could hold the links for milling a wrench hex, 1-5/8" material is too big for a Hardinge divider head.
The newer tool made perfect threads, infact I had some issues with the damn rodends not meeting industry spec on the threads, the pitch diameter was .005" under 2A tolerance low.

[TheBandit]

I got scared of cutting threads when I was doing my bender project, but the pics, info, and advice in this thread make it sound much more manageable.

Keep up the great work and thanks for sharing.

[MC]

I really like the insertable threading bars so your never grinding your tool. Good work on the bar though! Thats the sign of a good machinist.

[desertCJ]

We use a ID threading bar with indexable inserts as well, it's pretty nice, but for high quantity stuff, it's more of a pain to keep chasing the wear than it is using a tap.